SYNTHESIS OF NOVEL POLYESTERS AS PERFORMANCE ADDITIVES FOR TIRE TREAD COMPOUNDS

THIS PHD RESEARCH PROJECT WAS DEVELOPED THROUGH A COLLABORATION BETWEEN THE UNIVERSITY OF SALERNO AND PIRELLI TYRE S.P.A. THE CENTRAL OBJECTIVE OF THE COLLABORATION WAS THE SYNTHESIS OF NOVEL POLYESTERS TO BE EMPLOYED AS PERFORMANCE ADDITIVES FOR TIRE TREAD COMPOUNDS. IN THE CURRENT CONTEXT OF GROWING CONCERN ABOUT ENVIRONMENTAL POLLUTION, THE AUTOMOTIVE INDUSTRY DESERVES PARTICULAR ATTENTION, AS IT IS WIDELY REGARDED AS ONE OF THE MOST IMPACTFUL SECTORS AND RESEARCH IN THIS FIELD IS CRUCIAL TO DEVELOP MORE SUSTAINABLE SOLUTIONS. THIS PROJECT CONTRIBUTES TO THE IDENTIFICATION OF A NOVEL CLASS OF MATERIALS BASED ON POLYESTERS’ BLOCK COPOLYMERS OBTAINED FROM RING OPENING COPOLYMERIZATION OF EPOXIDES AND CYCLIC ORGANIC ANHYDRIDES PROMOTED BY BIS-THIOETHER-DIPHENOLATE-TYPE CATALYSTS. THE PROJECT PROGRESSED THROUGH SEVERAL STAGES, THE PRELIMINARY PHASE FOCUSED ON THE SYNTHESIS OF BIO-BASED MONOMERS AND COPOLYMERS, CARRIED OUT PRIMARILY IN THE LABORATORIES OF THE UNIVERSITY OF SALERNO AND, IN PART, AT THE TECHNICAL UNIVERSITY OF MUNICH. USING BIO-BASED EPOXIDES, THE CORRESPONDING COPOLYMERS WITH PHTHALIC ANHYDRIDE WERE OBTAINED, EXHIBITING TG RANGING FROM −30 °C TO +30 °C, DEPENDING ON MOLECULAR WEIGHTS BETWEEN 5,000 AND 20,000 DA. SUBSEQUENTLY, DI- AND TRIBLOCK COPOLYMERS WERE SYNTHESIZED, CYCLOHEXENE OXIDE (CHO) AND VINYLCYCLOHEXENE OXIDE (VCHO) WERE INCORPORATED TO OBTAIN POLYMER BLOCKS WITH DISTINCT RIGIDITY CHARACTERISTICS. THE MICROPHASE SEPARATION BEHAVIOR OF THE SYNTHESIZED COPOLYMERS WAS INVESTIGATED USING ATOMIC FORCE MICROSCOPY, WHICH PROVIDED INSIGHT INTO THE NANOSCALE MORPHOLOGY AND THE PHASE SEGREGATION BETWEEN THE SOFT AND HARD POLYMER DOMAINS. SUBSEQUENTLY, SELECTED COPOLYMERS WERE SUBJECTED TO AN EVALUATION OF THEIR DEGRADABILITY UNDER VARIOUS CONDITIONS. THE DEGRADATION PROCESS WAS MONITORED OVER TIME THROUGH GEL PERMEATION CHROMATOGRAPHY MEASUREMENTS, ENABLING THE DETERMINATION OF MOLECULAR WEIGHT REDUCTION. POLYESTERS’ NON-TOXICITY WAS CONFIRMED THROUGH CYTOTOXICITY ASSAYS PERFORMED ON HUMAN HEPATOCARCINOMA CELLS AND THE RESULTS DEMONSTRATED GOOD CELLS VIABILITY, INDICATING THAT THE MATERIALS ARE SUITABLE FOR ENVIRONMENTALLY SUSTAINABLE APPLICATIONS. FINALLY, THE SYNTHESIZED MATERIALS WERE EVALUATED FOR THEIR PERFORMANCE AS ADDITIVES IN TIRE TREAD FORMULATIONS. PRELIMINARY STUDIES WERE CONDUCTED USING COMMERCIAL POLYESTERS TO OPTIMIZE BOTH THE COMPOUND FORMULATIONS AND PROCESSING PARAMETERS. THE MODEL TREAD COMPOUNDS WERE PREPARED AND THEIR MECHANICAL PROPERTIES TESTED IN THE LABORATORIES OF PIRELLI TYRE S.P.A, THE RESULTS REVEALED THAT THE POLYESTER-BASED COMPOUNDS EXHIBITED PROMISING MECHANICAL PROPERTIES. ENCOURAGED BY THESE FINDINGS, THE COMPOUNDS WERE FURTHER SUBJECTED TO OZONE AGING TESTS TO EVALUATE THEIR OXIDATIVE STABILITY. REMARKABLY, THE POLYESTERS DEMONSTRATED A PROTECTIVE EFFECT AGAINST OZONE-INDUCED DEGRADATION, SUGGESTING THEIR POTENTIAL ROLE AS ANTIOXIDATIVE ADDITIVES. FOLLOWING THE ESTABLISHMENT OF SUITABLE FORMULATION AND PROCESSING PARAMETERS, THE SYNTHESIZED POLYESTERS WERE INCORPORATED INTO COMPOUNDS. THESE NEWLY DEVELOPED COMPOUNDS EXHIBITED COMPARABLE OR SUPERIOR MECHANICAL PROPERTIES, OZONE RESISTANCE, AND TUNABLE PERFORMANCES DIRECTLY CORRELATED TO THE MOLECULAR DESIGN AND PROPERTIES OF THE ADDITIVES. OVERALL, THE RESULTS PRESENTED IN THIS WORK DEMONSTRATE THAT THE SYNTHESIZED NOVEL BIO-BASED POLYESTERS ARE PROMISING CANDIDATES AS MULTIFUNCTIONAL ADDITIVES FOR TIRE TREAD FORMULATIONS. THEIR PERFORMANCE AS ADDITIVES IN TIRE COMPOUNDS OPENS NEW AVENUES FOR SUSTAINABLE MATERIAL DESIGN IN THE FIELD OF RUBBER COMPOUNDING AND GREEN TIRE TECHNOLOGY.